package lesson5;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;

public class UdpEchoServer{
    DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动--");
        while(true){
            //1读取请求
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            //2根据请求作出响应
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
            String response = process(request);
            //3发送给客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(), response.getBytes().length,
                    requestPacket.getSocketAddress());
            //4记录日志
            System.out.printf("[%s:%d] req: %s, resp: %s/n", requestPacket.getSocketAddress().toString(),
                    requestPacket.getPort(), request, response);
        }
    }

    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}

